Between 40% and 85% of women with Polycystic Ovary Syndrome (PCOS) are overweight or obese and obesity is closely linked to the development of PCOS. Although it is well established that obesity increases the severity of the clinical features of PCOS, data regarding the prevalence of PCOS in obese women and the change in body weight in women with PCOS over time are scares. In a prevalence study it was investigated whether obesity increases the risk of PCOS in the general population and they demonstrated that the prevalence rate of PCOS in underweight, normal-weight, overweight, and obese women were 8.2, 9.8, 9.9, and 9.0%, respectively, similar to that observed in the general population. These results suggest that the risk of PCOS is only minimally increased with obesity. On the other hand, in a Spanish prevalence study among overweight and obese subjects, they demonstrated a 28.3% prevalence of PCOS, which is markedly higher compared with the 5.5% prevalence of PCOS in lean women in Spain.